With the development of the display technology, the liquid crystal display panel possesses properties of small volume and light weight, low power consumption. Therefore, it has been favored by the users. The liquid crystal display device generally comprises the backlight module and the liquid crystal display panel. The backlight module is employed to provide the light for the liquid crystal display panel, and the liquid crystal display panel is employed to show information of words and images. In prior art, as executing the mass production of the liquid crystal panels, one liquid crystal display panel is first selected in general. The common voltage of this liquid crystal display panel is adjusted so that the display quality of the liquid crystal display panel reaches the best. For convenience, the common voltage of the liquid crystal display panel for now is the first common voltage. Then the common voltages of all the liquid crystal display panels in the mass production will be set to be the first common voltage. However, due to the factors with process difference of respective parts of the liquid crystal display panels, the common voltages which are required to be applied to the respective liquid crystal display panels will be different. Namely, as the first common voltage is applied to all the liquid crystal display panels in the mass production, the display qualities of the liquid crystal display panels in the mass production gets poor.